4b (diversity, selection and classification) Flashcards
what is diploid?
what is haploid?
2n chromosomes- 2 of each chromosome one from each parent
n number of chromosomes- one of each
what does fertilisation is random mean? what does it result in?
any sperm can fertilise any egg
results in zygotes w diff combo of chromosomes to both parents
what happens in meiosis?
interphase- DNA replication
Meiosis 1- homologous chromosomes separated from each other
meiosis 2- sister chromatids become separated
4 genetically different haploid cells are produced
what happens in meiosis 1?
prophase 1- nuclear envelope breaks down, spindle fibres form from centrioles, homologous chromosomes wrap around each other, crossing over occurs leading to variation
metaphase 1- chromosomes line up next to homologous partner at equator, centromeres attach to spindle fibres, chromosomes randomly organised on either side of equator- independent assortment leads to variation
anaphase 1- separation of homologous chromosomes to opposite poles, one of each pair will end up on either side so variation
telophase 1- reforming of the nuclear envelope
cytokinesis- cytoplasm splits
what happens in crossing over?
homologous chromosomes associate
chiasmata form
equal lengths of non-sister chromatids/ alleles are exchanged
producing new combinations of alleles
what happens in meiosis 2?
prophase 2- dna becomes condensed and visible again, nuclear membrane disintegrates, spindle fibres form, chromosomes are not identical
metaphase 2- chromosomes line up at centre attached by spindle fibres, randomly assorted to either side so variation
anaphase 2- genetically diff chromatids randomly segregated to opposite poles by spindle fibres contracting
telophase 2- nuclei reform
cytokinesis- cell splits, 4 cells, haploid
how does crossing over lead to variation?
in meiosis 1, homologous chromosomes pair up
chromatids twist around each other and bits of chromatids swap over
chromatids still contain same genes but diff combos of alleles
how does independent segregation lead to variation?
each homologous pair has 1 maternal and 1 paternal
when separated in meiosis1, chromosomes end up randomly in daughter cells
so 4 daughter cells have completely diff combos of maternal and paternal chromosomes
different outcome of meiosis/ mitosis
meiosis:
produces cells with half no of chromosomes as parent
daughter cells genetically diff from each other and parent
4 daughter cells
mitosis:
produces cells with same no of chromosomes as parent
daughter cells genetically identical to each other and parent
2 daughter cells
why are mules infertile?
metaphase 1, homologous chromosomes associate w each other to form bivalents but this can only happen if homologous chromosomes are similar size etc
donkey and horse chromosomes too diff to line up
also odd number so one is left unpaired
mitosis can still occur though as pairing up of homologous chromosomes is only in meiosis
what is a chromosome mutation?
variations in number of whole chromosomes or parts of chromosomes
caused by errors in meiosis
lead to inherited conditions as the errors are in gametes
example of chromosome mutation
non-disjunction
leads to down’s syndrome
chromosome 21 fails to separate properly in meiosis so one cell gets extra copy and one gets none
when this gamete fuses with another, results in 3 copies of chromosome 21
what is a mutation?
change in DNA base sequence
means amino acid sequence and protein are altered
(diff amino acid coded for so diff protein)
what is a mutagen?
eg
physical/ chemical agent that changes genetic material and increases frequency of mutations above normal background level
ionising radiation (gamma)
uv
nitrosamines in tobacco
viruses
mustard gas
benzene- industrial solvent
what is a substitution?
a single nucleotide base is replaced by another
what is a silent mutation?
no change to the primary structure of the polypeptide despite having change in base
due to degenerate nature of dna- substitution may still code for same amino acid
what is a deletion?
what effect does it have?
one base is deleted
knock on effect of all triplet codes
reading frame splits sequence into non-overlapping sections but deletion causes frame shift so every amino acid downstream of the mutation is effected.
what has happened if the chromosome number has halved?
meiosis
what has happened if the chromosome number has doubled?
fertilisation
what has happened if the chromosome number stays the same?
mitosis
what is non-disjunction?
the chromosomes fail to separate properly
what is aneuploidy?
the presence of an abnormal number of chromosomes in a cell eg having 45 or 47 chromosomes when 46 is expected in a human cell
What 4 things lead to variation?
2n possible combinations of maternal and paternal chromosomes
crossing over in meiosis 1
independent segregation in meiosis
random fusion of haploid gametes at fertilisation
what is genetic diversity?
number of different alleles of genes in a species or population
what is a population?
a group of organisms of one species living in a particular habitat
what is diversity within a population increased by?
mutations in dna forming new alleles
diff alleles being introduced into a population when individuals from another population migrate into them and reproduce- gene flow
what is a genetic bottleneck?
an event that causes a big reduction in a population eg when a large no of organisms in a pop die before reproducing
this reduces no of diff alleles in gene pool so decreases genetic diversity
survivors reproduce and larger pop created from few individuals
eg northern elephant seals
what is the founder effect? what can cause it to occur?
type of genetic bottleneck
few organisms from pop start new colony from small no of alleles in initial gene pool
frequency of each allele in new colony diff to frequency of those alleles in og pop. eg initially rare allele might become common now- may lead to higher incidence of genetic diversity
can occur due to migration leading to geographical separation or if new colony separated from og pop for another reason eg religion eg the amish
what is natural selection?
mutation may result in new allele that is beneficial (so different reproductive success) organism is better competetor and more likely to survive and reproduce and pass on useful allele so greater proportion of next gen have it so more likely to surive breed pass on so freq of allele increases from gen to gen leading to evolution
what are behavioural adaptations?
what are physiological adaptations?
what are anatomical adaptations?
examples
ways organisms act that increase chance of survival eg possums play dead if threatened
processes inside organisms body that increase chance of survival eg bears hibernate and lower rate of metabolism to conserve energy so dont need to eat
structural features of organisms body that increase chance of survival eg whales have blubber to keep warm
what is phylogeny?
what is a phytogenic tree?
study of evolutionary history of groups of organisms . tells us whos related and how closely
shows how all organisms adapted from one common ancestor
closely related species diverged away most recently so branches are closer together
what is taxonomy?
science of classification involves naming organisms and organising them into groups so easier to identify and study
how are organisms classified?
a hierarchy of groups with no overlaps
grouped according to evolutionary origins
what is a hierarchy
groups within groups with no overlap- belong to one group at each level
what are the three domains?
Eukaryota
bacteria
archaea
(booklet in book explaining each one. need to know?)
order of taxa
domain
kingdom
phylum
class
order
family
genus
species
what is a species?
group of similar organisms able to reproduce to give fertile offspring
what is the binomial naming system?
named by genus species so scientists across world can communicate
avoids confusion of common names
what is courtship behaviour?
what are the 2 types?
behaviour carried out by organisms to attract a mate of the right species
can be simple eg releasing chemicals or complex eg displays
what does courtship behaviour is species specific mean?
why is courtship behaviour species specific?
what can it be used for because of this?
only members of same species do and respond to that courtship behaviour
allows members of same species to recognise each other, prevent inbreeding and make reproduction more successful (check book for more)
can be used to classify organisms- more similar behaviour means more closely related
examples of courtship behaviour
fireflies-pulses of light- pattern specific to species
crickets make sounds- diff pattern diff species
male peacocks show off colourful tails
male butterflies use chemicals to attract females- only those of correct species respond
technologies useful for clarifying evolutionary relationships
genome sequencing
comparing amino acid sequence
immunological comparisons
how can genome sequencing be used to clarify evolutionary relationships?
can compare dna base sequence of one organism to that of another to see how closely related they are
more closely related -more similar order of bases
lead to reclassification of some animals
how can comparing amino acid sequence be used to clarify evolutionary relationships?
proteins made of amino acids
sequence of amino acids coded for by base sequence in dna
related organisms have similar amino acid sequences in proteins
how can immunological comparisons be used to clarify evolutionary relationships?
similar antibodies bind to same protein
antibodies of human version of a protein (anti-human antibodies) added to isolated sample of another species, any proteins like the humans will bind. more bound means more closely related
old ways of estimating genetic diversity vs new ways
- early estimates made by looking at frequency of measurable/ observable characteristics in a pop- alleles determine characteristics so wide variety of characteristics means lots of alleles so diverse
- now, gene technologies have been developed to measure directly and give more accurate estimate that can be compared easily:
- diff alleles have slightly diff base seq so compare base seq in diff organisms to see how many alleles of that gene in that pop
- diff alleles produce slightly diff mRNA seq and may produce proteins w diff amino acid seq so can be compared
what is variation?
what is it caused by?
difference that exists between individuals
genetic factors due to diff genes between species and diff alleles within species
differences in environment
most variation due to mix of both
why should you use a random sample when studying variation? how do you do this?
so its not biased and accurately represents whole population
eg pick random sample site by dividing field into coordinates and using number gen
what can we use to tell if theres variation between samples?
mean avg
most samples have values either side so end up with bell shaped normal distribution curve
what is standard deviation?
what are error bars?
tells u how much values in a sample vary- measure of spread of values about the mean
large sd- big variation vice versa
sd plotted on graph/ chart of mean values using error bars which extend 1 sd above and below mean- longer bar means larger sd so more spread out
what is biodiversity?
what is a habitat?
what is a community?
variety of living organisms in an area
place where an organism lives
all the populations of diff species in a habitat
what is local biodiversity?
what is global biodiversity?
variety of diff species in a small habitat
variety of species on earth
What is species richness?
how can it be worked out?
a measure of the number of different species in a community. it is a simple measure of diversity
worked out by taking random samples of a community and counting the no of diff species
other than species richness, what else is a measure of biodiversity?
Index of diversity which takes into account the number of species in a community (species richness) and the abundance of each species (population size)
how do you calculate the index of diversity?
d= N(N-1) / E n(n-1)
N is the total no of organisms of all species
n is the total number of organisms of 1 species
E is the sum of
higher number means more diverse. if all individuals are the same species the index of diversity is 1
Which agricultural practices reduce biodiversity?
woodland clearance- done to increase area of farmland but directly decreases no of trees and sometimes species of trees. destroys habitats so species lose shelter/ food and have to migrate/ die so biodiversity decreases
Hedgerow removal- done to increase area of farmland. same as woodland clearance
Pesticides- kills pests so directly reduce biodiversity and any species that feed on them lose food source so their number decrease too
Herbicides- kill weeds so decreases plant diversity and reduces no of organisms that feed on the weeds
monoculture- field of one type of plant. reduces biodiversity directly and also supports fewer organisms. also depletes soil of certain minerals. help- crop rotation
what are direct and indirect ways that farmers decrease biodiversity
direct:
remove hedgerows
woodland clearance
overgrazing
monoculture
pesticides directly kill pests
herbicides
indirect:
pesticides kill animals that feed on pests
inorganic fertilisers
effluent runoff into water
not rotating crops
examples of conservation schemes to protect biodiversity
giving legal protection to endangered species as well as breeding programmes
creating protected areas such as SSSIs (sites of special scientific interest) and AONBs (areas of outstanding natural beauty). these restrict further development
the environmental stewardship scheme encourages farmers to conserve biodiversity eg by replanting hedgerows
reduction of CO2 emissions and deforestation by some governments
what is directional selection?
eg?
individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. could be resopnse to change in environment
eg bacteria evolving antibiotic resistance- some have alleles giving them ar, pop exposed to antibiotic which kills bacteria wo ar, resistant survive and pass on useful allele so offspring have ar, after some time, most of pop will carry ar allele
what is stabilising selection?
eg?
individuals with alleles for characteristics towards the middle are more likely to survive and reproduce. occurs when environment isnt changing and reduces range of poss characteristics
eg human birth weight- humans have range of birth weights but very small are less likely to survive as its hard to maintain body temp and large babies are less likely to survive as hard to birth. medium sized is most favourable so weight of human babies tends to shift to middle
what is disruptive selection?
eg?
favours the 2 extremes of a phenotype. occurs in environ that favours more than one phenotype. selection pressures select against avg phenotype
eg Atlantic salmon, coloured oysters
what is dna hybridisation?
what are the steps of dna hybridisation?
- used to compare dna of 2 species to see how closely related they are
1) take dna from 2 species and radioactively label 1 and mix the 2 species
2) heat to break H bonds and separate strands. - let them cool so strands can combine w others with complimentary sequence
3) some double strands that reform will be hybrids
4) more complimentary the hybrid dna sequence, more H bonds as more complimentary so higher temp needed to separate the H bonds
5) higher the temp. more similar the base sequence so more closely related
practical in this topic?
aseptic technique
